In order to help with the conference costs and attendance, SPIE adjoined the Scanning Microscopies conference with BACUS this year. One of the more interesting papers, given in a joint session between SEM and BACUS, concerned 3D SEM metrology at the 10 nm scale. The speaker pointed out that three operational steps are required to obtain sub-nm resolution:
- First, the obvious, tune up the SEM (focus, stigmation, …).
- Second, eliminate all contamination (H2 plasma) to prevent (hydro)carbon coating. This stabilizes the image and prevents it washing out during the observation.
- Third, acquire the image not with slow scans, but with many, very rapid scans. These scans must be aligned digitally, thereby eliminating effects of drift, vibration, and stray magnetic fields. In regard to this third step, NIST recommends heavier algorithm development for SEM metrology. Further details may be found in a NIST paper from the SEM conference.
Under these conditions, one sees excellent 3D images. In fact, the speaker passed around 3D glasses so that one could view 3D images on the conference room screen.
Given that SEM and BACUS ran in mostly parallel sessions, it was difficult to get much of the hoped-for mixing between disciplines. No doubt SPIE realized better space utilization at the conference center.